1. Field of the Invention
This invention relates to measuring product parameters within a manufacturing line such as a semiconductor process line, detecting statistical deviations and faults of various processes within the manufacturing line, and notifying appropriate control personnel of the process variations and faults.
2. Description of Related Art
In manufacturing processes such as fabrication of integrated circuits on a substrate, numerous process steps are necessary to fabricate the product such as wafers containing many integrated circuit chips. In the processing of integrated circuits, the yield is sensitive to the performance of the equipment performing the processes. The yield is detected by measuring the electrical performance of the integrated circuits and examination of the substrate for defects.
Generally, the substrates are fabricated with test structures being placed in the “scribe-line” between each of the integrated circuit chips. The test structures are probed and subjected to appropriate electrical and environmental stress to verify that the performance of the wafer will meet the objectives of the design. Further the wafers are scanned to detect physical defects that indicate a failure in the fabrication of the integrated circuit upon the wafer. These process monitoring and inspection tests generally capture failures and deviations of process equipment. However, it is well known in the art that certain process variations are not detected with process monitoring and inspection described. Certain equipment problems appear only with particular specific product design parameters and then are only evident from examination of long term parametric testing.
U.S. Pat. No. 5,923,553 (Yi) describes a method for controlling a semiconductor manufacturing process by failure analysis feedback. The method compares a previous failure analysis result with current real-time process conditions. The method begins by establishing a monitoring data base with abnormal process condition data, the abnormal process condition data being obtained by a correlation between a yield for each manufactured lot and corresponding process conditions for semiconductor equipment when the yield is lowered or semiconductor equipment malfunctions have occurred. An equipment database is then established by obtaining real-time process conditions for on-line semiconductor equipment. The real-time process conditions for the on-line semiconductor equipment are compared with the abnormal process conditions of the monitoring database. The operation of the on-line semiconductor equipment is then stopped when differences between the real-time and abnormal process conditions fall below a predetermined level.
U.S. Pat. No. 5,956,251 (Atkinson, et al.) teaches a process of establishing valid statistical dimensional tolerance limits for designs of detail parts. The process enables accurate prediction of an economically acceptable degree of non-conformance of a large flexible end item assembly made from the detail parts. The end item assembly has a set of predetermined dimensional tolerances. The detail part tolerances are enlarged substantially compared to tolerances that would be necessary using an arithmetic “worst case” approach to remain within the end assembly tolerances while remaining within preestablished stress limits of the parts. A preferred assembly sequence for assembling the parts into the assembly is selected and validated. Locations, numbers and size of coordination features to be machined in the detail parts are selected, by which the parts are located relative to each other and fastened together to form the assembly. Individual part statistical dimensional tolerances are established as a fabrication requirement for the parts that enable the parts to be economically produced and assembled into assemblies that meet the predetermined assembly dimensional tolerances. The parts are produced to the individual statistical dimensional tolerances in a capable process, having a process capability index equal to at least 1.0, while holding the mean values of the statistically determined dimensions of the individual parts to within a predetermined percentage of the nominal dimension. The end item is assembled in accordance with the preferred assembly sequence by locating the parts relative to each other by reference to the coordination features as the primary determinator of assembly configuration.
U.S. Pat. No. 6,304,791 (Kim) describes a method for controlling semiconductor equipment interlocked with a host computer. The method allows prevention of an operator from accidentally operating a piece of equipment, which is in an interlocked state. A host computer automatically stores information on any interlocked piece of equipment, and rechecks that information before allowing any product to be introduced into a piece of equipment. Optimal process conditions for each process are registered in the host computer. The registered optimal process condition is compared with process data reported from each piece of equipment. If it is determined that the reported data are in the range of the optimal process conditions in view of the comparison, it is then determined whether or not the reported data also satisfy a specific rule registered in the host computer. If it is determined that the reported data satisfy the specific rule, the process continues. Otherwise, if it is determined that the reported data do not satisfy the specific rule, the equipment and a tracking module of the host computer are simultaneously interlocked and the interlocking is automatically saved in the host computer. The process is stopped until the process failure is solved.
U.S. Pat. No. 5,862,054 (Li) teaches a process monitoring system for real time statistical process control. The method monitors process parameters from multiple process machines to provide real time statistical process control (SPC). The particular implementation was derived from ion implantation of wafers, but has wide applicability where there are a number of process machines having a number of process parameters and close continuous sampling of data is required. The process parameters are collected on a single computer over a single RS 485 network, and each parameter is analyzed and displayed separately for each process and process machine. Statistical variables like capability ratio and process capability index are calculated and presented on the computer screen along with graphs of the various parameters for a particular process machine. Data is aged out of the computer to an archival database under the control of a manufacturing information system and connected to a company wide network.